Wheel frame for a skateboard

ABSTRACT

An improved wheel frame for a skateboard, wherein slipping wheels connect with a skateboard body stably, comprises: a wheel frame main body having a screw hole on each side; two wheel axles for screwing in the screw hole of the wheel frame main body, wherein in each axle a through hole is set, the through hole has at least one longitudinal expansion joint in the thread for flexible expanding the diameter; and an expansion element for setting in the through hole of the both axles, wherein the diameter of the thread within the axle is forced to expand, so that the thread of the axles and the screw holes of the wheel frame main body are firmly held together.

FIELD OF THE INVENTION

The present invention relates to an improved wheel frame for is skateboard, particularly to a wheel frame for a skateboard applied to extreme sports.

BACKGROUND OF THE INVENTION

Skateboarding is a kind of popular sports, which spread to all countries. Time and again new skills and pop elements are added in skateboard sports. Therefore the manufacturers endeavor again and again to make improvements and innovations.

As shown in FIG. 6, a conventional skateboard comprises: a board body 1 made of light and highly strong material, like wood, plastic, carbon fiber and glass fiber; and two wheel frames 2 (only one wheel frame 2 shown) set on both ends of the board body 1, wherein a pair of slipping wheels 3 are mounted on each wheel frame 2 for slipping on the floor.

As shown in the FIGS. 6 and 7, a conventional skateboard wheel frame 2 has a T-shaped form, wherein there is a tube hole for putting through an axle 4. The axle 4 is an rod in one piece, wherein after putting through in the wheel frame 2 both ends of the axle protrude outside on both ends of the wheel frame 2, and the slipping wheels 3 are mounted on the protruding ends of the axle 4.

As shown in FIG. 7, in conventional art, for fixing the axle 4 in the wheel frame 2, there is a longitudinal thread 5 surrounding the end of the axle 4 on an outside thereof near the end of the wheel frame 2, wherein the longitudinal thread 5 protrudes from the surface of the axle, thus the diameter of the longitudinal thread 5 is larger than that of the other part of the axle 4. The diameter of the tube hole for the axle 4 to set through in the wheel frame 2 is larger than the diameter of the axle 4 and smaller than that of the longitudinal thread 5. Therefore, as the axle 4 is set in the wheel frame 2, one can use a tool to press the longitudinal thread 5 of the axle 4 into the tube hole or the wheel frame 2, so the axle 4 and the tube hole of the wheel frame 2 occlude firmly through the longitudinal thread 5, and is fixed in the tube of the wheel frame 2, not being able to rotate. Stable locating and support of the slipping wheels are achieved.

However, a conventional wheel frame for skateboards still has several disadvantages. Firstly, only on the one end of the axle 4 with the longitudinal thread 5 occluding the tube hole of the wheel frame 2 is a stable locating achieved, while the other end without longitudinal thread gets gaps therebetween which resulting swaying. Hence, if slipping wheels on the unoccluded end of axle are loaded, the right and left slipping wheels are not in balance and swaying occurs easily. Axial movement bring the axle to loose from the wheel frame, with potentially dangerous results.

In conventional art, a hollow structure or light metal materials like titanium alloy are used for lightening the axle 4. However, since the axle 4 has a large length, manufacturing of a hollow structure is difficult and expensive. In case titanium is used, the costs of material increase. Accordingly, a conventional wheel frame for skateboard needs high costs for lightening.

According to the reasons mentioned above, a conventional wheel frame for skateboard still has disadvantages and needs improvement.

SUMMARY OF THE INVENTION

The main objects of the present invention are to provide a wheel frame for a skateboard, wherein swaying and loosening occuring by axle fixation in a conventional wheel frame for a skateboard are reduced and wherein the problem of lightening the axle is solved.

In the present invention, the axle is converted into two parts, which are locked on the both ends of the wheel frame. At the same time, the threads of both axles are designed as hollow and expandable structure, wherein a expansion element is set at the center for extending the diameter of the thread in the axles and thereby occluding with the screw hole in the wheel frame, so that both axles neither loosen nor rotate. Accordingly, a stable setting of the both axles in a wheel frame is achieved.

In the present invention the axles on each end of the wheel frame are stably set in the frame body, so swaying and loss of balance of the slipping wheels caused by unstable fixation of the axles are avoided. The two axles are shorter then a conventional one-piece axle, thereby material consumption is reduced and costs for manufacturing a hollow structure are reduced. Hence lightening of the axle is achieved.

Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the wheel frame main body of the present invention.

FIG. 2 is a perspective view of the axle of the present invention.

FIG. 3 is a sectional view of the axle of the present invention, showing the internal structure of the axle.

FIG. 4 is an exploded view of the present invention.

FIG. 5 is a partial sectional view of the present invention, showing the assembly of axle and wheel frame.

FIG. 6 is a perspective view of a conventional wheel frame for a skateboard.

FIG. 7 is a side view of an axle of a conventional wheel frame for a skateboard.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1 to FIG. 5, the improved wheel frame for a skateboard 100 of the present invention comprises: a wheel frame main body 10 having a T-shaped form with a shaft hole 11 at the center and two screw holes 12 set symmetrically on each ends; two wheel axles 20, which are screwed in the screw holes 12 of the wheel frame main body 10 and protrude beyond both ends of the wheel frame main body 10, for setting the slipping wheels of skateboard (not shown) on both ends of the wheel frame main body.

As shown in FIG. 2 and FIG. 3, the wheel axle 20 of the present invention having a rod-shaped form comprises: a rod-shaped middle part 21 as well as a first end 22 and a second end 23 on both ends of the middle part 21. Outside the first end 22, there is a thread 24 matching with the screw holes 12 on each end of the wheel frame main body 10 for screwing in. Outside the second end 23, there is a second thread 25. As shown in FIGS. 4 and 5, after the first end of the axle 20 is screwed in the screw hole 12 of the wheel frame main body 10, the middle part 21 protrudes on both ends of the wheel frame main body 10, for mounting the slipping wheels of the skateboard thereon. Besides, a nut is screwed in the second thread 25 (not shown), so that the slipping wheels are fixed on the axle 20.

As shown in FIG. 4 and FIG. 5, the wheel axles 20 are characterized by a through hole 26 being set in the center of the wheel axle 20, hence a hollow structure is formed. On the first end 22 of the wheel axle 20, there is at least one longitudinal expansion joint 27, wherein the diameter of the first end 22 is expandable; the diameter of the through hole 26 on the first end is slightly narrowed, thereby a stage part 28 results. Besides, within the wheel axle 20 an expansion element 30 is set in. The expansion element 30 is a cylinder, whose diameater is slightly larger then the internal diameter of the stage part 28 and which has a cone 31 on one end.

As shown in FIG. 5, after the first end 22 of the wheel axle 20 is screwed in the screw hole 12 of the wheel frame main body 10, the expansion element 30 is put in the through hole 26 and, using a tool, the expansion element 30 is pressed in the stage part 28 of the through hole 26. Since the stage part 28 is pressed by the expansion element 30, the external diameter of first end 22 is forced to expand, thereby the wheel axle 20 is matched firmly with the screw hole 12 of the wheel frame main body 10.

By the effects of the expansion joint 27 and the expansion element 30, both wheel axles are stably fixed in the screw hole 12, hence the both wheel axles 20 are stably set on the both ends of the wheel frame main body 10.

Im comparison to prior art, the axles of the present invention are a separated structure in two pieces, wherein the length of both axles 20 measures only one third, as compared to prior art, moreover it is a hollow structure, thus the total weight is reduced.

Furthermore, both wheel axles 20 are firmly fixed in the screw holes 12 of the wheel frame main body 10 through the expansion element 30. Additionally, the both axles 20 are fixed with the wheel frame main both 10 in the same way, wherein the force keeps balance; unlike the wheel axles of a conventional skateboard, wherein only one end is fixed on the wheel frame, while on the other end gaps easily cause swaying and loosing under stress. 

1. An improved wheel frame for a skateboard, wherein slipping wheels connect with said skateboard body stably, comprising: a wheel frame main body, which is set under said skateboard body, having a slipping wheel on each end; characterized by: said wheel frame main body having a screw hole on each end and two wheel axles, which are firmly screwed on both ends in said wheel frame main body for mounting said slipping wheel.
 2. The improved wheel frame for a skateboard of claim 1, wherein each wheel axle has a first end with a thread on an outer side for screwing in said screw hole on each end of said wheel frame main body.
 3. The improved wheel frame for a skateboard of claim 2, wherein each wheel axle has a through hole at said center for forming a hollow structure.
 4. The improved wheel frame for a skateboard of claim 3, wherein said wheel axle at said first end has at least one longitudinal expansion joint, and said through hole at said position of said first end has a stage part with a narrower diameter.
 5. The improved wheel frame for a skateboard of claim 4, wherein in said through hole of said wheel axle an expansion element having a larger diameter than that of said stage part is set; if said expansion element is pressed in said stage part, said external diameter of said first end is forced to expand and thereby said thread of first end and said screw hole of said wheel frame main body occlude firmly.
 6. The improved wheel frame for a skateboard of claim 5, wherein said expansion element is a cylinder with a cone on one end.
 7. The improved wheel frame for a skateboard of claim 1, wherein each wheel axle has a through hole at said center for family a hollow structure.
 8. The improved wheel frame for a skateboard of claim 7, wherein said wheel axle at said first end has at least one longitudinal expansion joint, and said through hole at said position of said first end has a stage part with a narrower diameter.
 9. The improved wheel frame for a skateboard of claim 8, wherein in said through hole of said wheel axle an expansion element having a larger diameter than that of said stage part is set; if said expansion element is pressed in said stage part, said external diameter of said first end is forced to expand and thereby said thread of first end and said screw hole of said wheel frame main body occlude firmly.
 10. The improved wheel frame for a skateboard of claim 9, wherein said expansion element is a cylinder with a cone on one end. 